WASHINGTON – In a farewell letter, ousted Attorney General Jeff Sessions Thursday characterized his often-tumultuous tenure an “incredible honor” and urged colleagues to remain true to the Justice Department’s core mission to “protect the American people and the rights we hold dear.”

Sessions never referred to President Donald Trump, who abruptly dismissed the former Alabama senator Wednesday following months of unrelenting criticism. The president installed Sessions’ chief of staff, Matthew Whitaker, to serve as acting attorney general.

Instead, the 84th attorney general expressed general gratitude to the sprawling department’s 115,000 staffers for confronting such challenges as violent crime enforcement and the opioid crisis.

“We have the most fundamental and the most sacred task of government: to secure the equal rights of the citizens of this country,” Sessions wrote. “Every other initiative of government depends upon us doing our jobs successfully.”

One of Trump’s earliest supporters, Sessions, a former federal prosecutor, described his appointment as the nation’s chief law enforcement officer as “beyond anything I ever would have thought possible.”

“If you had told me when I was starting out as a young assistant United States attorney that I would ever serve as attorney general, I don’t think I would have believed you,” he said.

That tenure, however, would often prove to be a test of Sessions’ endurance.

Sessions’ relationship with Trump, once celebrated by the then-Republican candidate, quickly soured after the attorney general recused himself from overseeing the ongoing investigation into Russia’s meddling in the 2016 election.

Its lowest point came in September, when Trump – again lamenting the looming Russia investigation – declared: “I don’t have an attorney general. It’s very sad.”

Despite every jab, Sessions only pressed.

“No matter what your role at the department and no matter what your task, I hope that you will remember that you are helping us in our mission to protect the American people and the rights we hold dear,” Sessions wrote.

“I am grateful to have served with people of your caliber and may God bless you and your families in all you do. Keep improving, getting better and more productive.”